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fix_gravity.cpp
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Sat, Aug 10, 05:26

fix_gravity.cpp
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/* ----------------------------------------------------------------------
LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
http://lammps.sandia.gov, Sandia National Laboratories
Steve Plimpton, sjplimp@sandia.gov
Copyright (2003) Sandia Corporation. Under the terms of Contract
DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
certain rights in this software. This software is distributed under
the GNU General Public License.
See the README file in the top-level LAMMPS directory.
------------------------------------------------------------------------- */
#include "math.h"
#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "fix_gravity.h"
#include "atom.h"
#include "update.h"
#include "domain.h"
#include "respa.h"
#include "error.h"
using namespace LAMMPS_NS;
enum{CHUTE,SPHERICAL,GRADIENT,VECTOR};
/* ---------------------------------------------------------------------- */
FixGravity::FixGravity(LAMMPS *lmp, int narg, char **arg) :
Fix(lmp, narg, arg)
{
if (narg < 5) error->all("Illegal fix gravity command");
time_depend = 1;
magnitude = atof(arg[3]);
if (strcmp(arg[4],"chute") == 0) {
if (narg != 6) error->all("Illegal fix gravity command");
style = CHUTE;
phi = 0.0;
theta = 180.0 - atof(arg[5]);
} else if (strcmp(arg[4],"spherical") == 0) {
if (narg != 7) error->all("Illegal fix gravity command");
style = SPHERICAL;
phi = atof(arg[5]);
theta = atof(arg[6]);
} else if (strcmp(arg[4],"gradient") == 0) {
if (narg != 9) error->all("Illegal fix gravity command");
style = GRADIENT;
phi = atof(arg[5]);
theta = atof(arg[6]);
phigrad = atof(arg[7]);
thetagrad = atof(arg[8]);
} else if (strcmp(arg[4],"vector") == 0) {
if (narg != 8) error->all("Illegal fix gravity command");
style = VECTOR;
xdir = atof(arg[5]);
ydir = atof(arg[6]);
zdir = atof(arg[7]);
} else error->all("Illegal fix gravity command");
double PI = 2.0 * asin(1.0);
degree2rad = 2.0*PI / 360.0;
if (style == CHUTE || style == SPHERICAL || style == GRADIENT) {
if (domain->dimension == 3) {
xgrav = sin(degree2rad * theta) * cos(degree2rad * phi);
ygrav = sin(degree2rad * theta) * sin(degree2rad * phi);
zgrav = cos(degree2rad * theta);
} else {
xgrav = sin(degree2rad * theta);
ygrav = cos(degree2rad * theta);
zgrav = 0.0;
}
} else if (style == VECTOR) {
if (domain->dimension == 3) {
double length = sqrt(xdir*xdir + ydir*ydir + zdir*zdir);
xgrav = xdir/length;
ygrav = ydir/length;
zgrav = zdir/length;
} else {
double length = sqrt(xdir*xdir + ydir*ydir);
xgrav = xdir/length;
ygrav = ydir/length;
zgrav = 0.0;
}
}
time_origin = update->ntimestep;
}
/* ---------------------------------------------------------------------- */
int FixGravity::setmask()
{
int mask = 0;
mask |= POST_FORCE;
mask |= POST_FORCE_RESPA;
return mask;
}
/* ---------------------------------------------------------------------- */
void FixGravity::init()
{
if (strcmp(update->integrate_style,"respa") == 0)
nlevels_respa = ((Respa *) update->integrate)->nlevels;
dt = update->dt;
xacc = magnitude*xgrav;
yacc = magnitude*ygrav;
zacc = magnitude*zgrav;
}
/* ---------------------------------------------------------------------- */
void FixGravity::setup(int vflag)
{
if (strcmp(update->integrate_style,"verlet") == 0)
post_force(vflag);
else {
((Respa *) update->integrate)->copy_flevel_f(nlevels_respa-1);
post_force_respa(vflag,nlevels_respa-1,0);
((Respa *) update->integrate)->copy_f_flevel(nlevels_respa-1);
}
}
/* ---------------------------------------------------------------------- */
void FixGravity::post_force(int vflag)
{
// update direction of gravity vector if gradient style
if (style == GRADIENT) {
if (domain->dimension == 3) {
double phi_current = degree2rad *
(phi + (update->ntimestep - time_origin)*dt*phigrad*360.0);
double theta_current = degree2rad *
(theta + (update->ntimestep - time_origin)*dt*thetagrad*360.0);
xgrav = sin(theta_current) * cos(phi_current);
ygrav = sin(theta_current) * sin(phi_current);
zgrav = cos(theta_current);
} else {
double theta_current = degree2rad *
(theta + (update->ntimestep - time_origin)*dt*thetagrad*360.0);
xgrav = sin(theta_current);
ygrav = cos(theta_current);
}
xacc = magnitude*xgrav;
yacc = magnitude*ygrav;
zacc = magnitude*zgrav;
}
double **f = atom->f;
double *rmass = atom->rmass;
double *mass = atom->mass;
int *mask = atom->mask;
int *type = atom->type;
int nlocal = atom->nlocal;
double massone;
if (rmass) {
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
massone = rmass[i];
f[i][0] += massone*xacc;
f[i][1] += massone*yacc;
f[i][2] += massone*zacc;
}
} else {
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
massone = mass[type[i]];
f[i][0] += massone*xacc;
f[i][1] += massone*yacc;
f[i][2] += massone*zacc;
}
}
}
/* ---------------------------------------------------------------------- */
void FixGravity::post_force_respa(int vflag, int ilevel, int iloop)
{
if (ilevel == nlevels_respa-1) post_force(vflag);
}

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